BEFORE you start eating say this dua:

“Bismillahi wa alaa barkatillah”Which Means – “In the name of Allah and upon the blessings of Allah”. (Al Hisnul Haseen Page 141)

If you forget to recite dua beforeyou begin to eat then say :

“Bismillahi awwalahu wa aakhirahu”Which means “In the name of Allah in the beginning and the end”. [Abu Dawood Vol 2 Page 173]